Calvin Coolidge

Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent.

Hammer down product fundamentals first. Make sure you've got something that works before doubling down on promotion and marketing. Create a groundswell of organic support, and only then leverage PR and advertising to spread the word.